**The Solar Wind Elemental Composition**

46 Exploring the Solar Wind

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**3** 

**Solar Wind Composition** 

X. Wang1, B. Klecker2 and P. Wurz3

*The National Astronomical Observatories,* 

*2Max-Planck-Institut für Extraterrestrische,* 

*3Physikalisches Institut, Universität Bern, Bern* 

*1Key Laboratory of Solar Activity,* 

*CAS, Chaoyang District, Beijing* 

*Physik, Garching* 

*1P.R. China 2Germany 3Switzerland* 

**Associated with the Solar Activity** 

The studies of elemental abundance of solar wind ions allows to address by open questions in several major fields of research: solar physics, heliospheric and planetary physics, and astrophysics and cosmology. This chapter is intended to provide the current status of knowledge about the solar wind composition mainly in relation to the solar physics with the

The composition of the solar wind is mainly determined by the composition of the source material at the solar surface, and then modified by plasma processes in the solar atmosphere, operating in the transition region and in the inner corona. In recent decades, attention in composition studies has shifted from its early models toward differences in chemical fractionation as well as considerable fine-structure in the region above the solar surface. In-situ measurements of the solar wind composition give a unique opportunity to obtain information on the isotopic and elemental abundances of the Sun (e.g. Bochsler,

The magnetic field on the surface and in the atmosphere of the Sun is considered by many to play a significant role in the plasma processes, which is reflected in composition changes. The magnetic field on the solar surface includes two components: open magnetic flux, which opens into the heliosphere to form the heliospheric magnetic field (also called the interplanetary magnetic field); and closed magnetic flux, in the form of loops attached at both ends to the solar surface. The open magnetic flux controls many of the important processes in the solar corona. Reames (1999) argues that the interaction of loops with open flux is essential for an impulsive solar particle event, i.e., magnetic field reconnection causing the re-distribution of the magnetic field in the loop, the transfer of magnetic energy to the local plasma, and the escape of energetic particles. The interaction and reconnection

**1. Introduction** 

1998).

emphasis on the effects of solar magnetic field.
